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Showing posts from November, 2010

Brake lights sensitive to braking force

Almost every time I sit in the co-driver's seat in a car, I get a feeling of fear and claustrophobia whehever the car at the front starts braking. I feel like the car in front may be braking more abruptly than the car I am sitting in. Hence, I squinch expecting a crash, which gladly has not happened yet.
The red braking ligths are scary. While their purpose is to inform the drivers behind that the car is braking, it fails at telling how much it is braking. Because one can't know for sure if the car is braking abruptly or just sligthy, the back driver may push the braking pedal stronger or with less force than needed, causing a car crash.
Hence, I have thougth of a solution: force sensitive braking lights. The idea is that the light is brigther when the braking force is larger and weaker when the braking force is smaller. However, it cannot be made just that simple. For the back driver to know how much the front car is braking, two characteristics are required: the current bra…

Digit sums of multiples of 11

"Some multiples of 11 have an even digit sum.  For example, 7*11 = 77 and 7+7 = 14, which is even; 11*11 = 121 and 1+2+1 = 4, which is even.  Do all multiples of 11 have an even digit sum?  (Prove that they do or find the smallest that does not.)"(Source)
To practice my Java programming skills (I've began learning Java about a month ago) I wrote a small program that finds all the numbers for which the statement does not hold.
The output looks like this:
> run Multilpe11 Some multiples of 11 have an even digit sum.  For example, 7*11 = 77 and 7+7 = 14, which is even; 11*11 = 121 and 1+2+1 = 4, which is even.   Do all multiples of 11 have an even digit sum?  (Prove that they do or find the smallest that does not.) For how many consecutive multiples of 11 would you like to check if the statement is correct:  1000 These are 36 numbers smaller than 1000, that are multiples of 11, but whose digit sum is not even. These numbers are: 209 308 319 407 418 429 506 517 528 53…